The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, HDDs have been desired to store more information in a limited area and volume. A technical approach to meeting this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
Magnetoresistive effect type magnetic heads are employed as sensors for reading magnetic information (data) recorded on a magnetic recording medium (such as a hard disk) in high-density magnetic recording devices (such as HDDs). The use of magnetic read heads that utilize a magnetoresistive effect has become commonplace. One such magnetoresistive effect type read head uses a giant magnetoresistive (GMR) effect in a multi-layered film formed by laminating a ferromagnetic metal layer on a non-magnetic intermediate layer. The first kind of GMR heads employed were Current-In-Plane (CIP)-type heads in which electrical signals flow in parallel with the film plane to the sensor membrane. Next, Tunneling Magnetoresistive (TMR)-effect heads and Current-Perpendicular-To-Plane (CPP)-GMR heads, which are considered advantageous from the standpoint of track narrowing, gap narrowing, and increased output, were developed with improved recording density in mind.
While the demand in recent years for even higher density recording has been met by techniques based on narrowing the effective track width of a magnetoresistive sensor, this track width narrowing has resulted in other problems of increased element resistance, increased noise, lowered sensitivity, and difficulties in increasing the sensitivity.
Multi-element reader structures designed to accommodate higher density recording have been proposed to alleviate these problems. Multi-element readers are advantageous in that they allow for a magnetic head with a large number of elements of a size greater than a bit size of the medium, and this allows for bit data to be read from the difference in the plurality of signals produced thereby. Because the element size may be increased beyond a single bit size, noise is able to be suppressed and sensitivity is able to be increased. However, multi-element readers have high interconnection resistance, so the signal-to-noise ratio (SNR) of these readers is low, in comparison to typical single element readers, due in major part to resistance noise.
Single sensor reader structures connect using a wide upper shield, so interconnection resistance of a single sensor reader is low. However, multi-sensor readers are not able to utilize the same connection point using the upper shield, therefore multi-sensor readers connect via individual current path layers. As a result, interconnection resistance for the multi-sensor readers is high in comparison to single-sensor readers.